if __name__ == "__main__":
    with arcpy.da.SearchCursor("c:\temp.gdb\test", fields=["*"]) as s_cursor:
        pool = multiprocessing.Pool(processes=4)  # lets use 4 workers
        cursor_iterator = iterator_slice(s_cursor, 100)  # slicer from above, for convinience
        queue = []  # a queue for our current worker async results, a deque would be faster
        while cursor_iterator or queue:  # while we have anything to do...
            try:
                # add our next slice to the pool:
                queue.append(pool.apply_async(insert, [next(cursor_iterator)])) 
            except (StopIteration, TypeError):  # no more data, clear out the slice iterator
                cursor_iterator = None
            # wait for a free worker or until all remaining finish
            while queue and (len(queue) >= pool._processes or not cursor_iterator):
                process = queue.pop(0)  # grab a process response from the top
                process.wait(0.1)  # let it breathe a little, 100ms should be enough
                if not process.ready():  # a sub-process has not finished execution
                    queue.append(process)  # add it back to the queue
                else:
                    # you can use process.get() to get the result if needed
                    pass
        pool.close()